In 1919 a total solar eclipse allowed Arthur Eddington to put Einstein's general theory of relativity to the test to see if the Sun's mass was really warping spacetime, deflecting the light from faraway stars. A team of scientists is now looking for general relativitistic phenomena using not the Sun, but the Earth — and adding rotational effects into the mix.
Using ring laser gyroscopes — essentially optical interferometers placed in a ring configuration — Jacopo Belfi and colleagues are hoping to detect a gravitomagnetic effect known as the Lense–Thirring effect. Arising from the Earth's mass and angular momentum, this general relativitistic phenomenon should cause a difference between the rotation rate of the Earth measured by a ground-based observatory and the value measured in an inertial reference frame.
In order to achieve the resolution required to see such effects, the team have gone deep underground in the international laboratory of Gran Sasso in central Italy, far away from external disturbances. And they have now made an important step towards their goal by demonstrating a pilot prototype, known as GINGERino, which can make Earth rotation measurements, as well as act as a seismic observatory.
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Fleet, L. Going underground. Nature Phys 13, 321 (2017). https://doi.org/10.1038/nphys4097